Machine for cutting leaf tobacco



May 30, 1967 H. WARD 3,322,175

MACHINE FOR CUTTING LEAF TOBACCO Filed March 30, 1964 Inventor A4 4 my (4144i.

A ltorneys &

United States Patent Ofiice 3,322,175 Patented May 30, 1967 3,322,175 MACHINE FOR CUTTING LEAF TOBACCO Harry Ward, London, England, assignor, by mesne assignments, to AMF International Limited, London, England Filed Mar. 30, 1964, Ser. No. 355,801 Claims priority, application Great Britain, Mar. 28, 1963, 12,375/63 Claims. (Cl. 146121) This invention is concerned with a rotating cutter which is particularly suitable as a component of a tobacco cutting machine in which tobacco is fed between conveyors to a mouthpiece, through which it passes in order to be cut by knives mounted upon the rotating cutter, the knives having cutting edges which move in a cylindrical path which touches or nearly touches the front face of the mouthpiece. Such a machine is described in British Patent No. 751,093 for example.

The invention is particularly concerned with an improved arrangement for gripping the knives of such a rotating cutter, so that they are firmly secured to a substantially cylindrical drum in order to form the cutter. It is required that the knives should be firmly gripped by friction, in order to resist the cutting forces as well as the considerable stresses set up when a knife strikes mineral fragments in the tobacco, and yet should be able to be fed forward progressively and with absolute certainty a distance of precisely 0.001 inch per minute, for example. An arrangement for feeding the knives forward progressively is described in Patent No. 751,015.

According to the invention, a drum rotatable about an axis and having a clamping surface associated with it, a knife, an outer plate having a heel portion and a toe portion, a base plate fixed in relation to the drum, and means for clamping a clamping surface on the heel portion of the outer plate against the clamping surface on the drum, so that the knife is gripped between a clamping surface on the toe portion of the outer plate and the base plate with a gripping pressure due to flexure of the outer plate, and the cutting edge of the knife projects slightly beyond the toe portion of the outer plate.

In the preferred arrangement, the clamping surface associated with the drum is formed on a heel plate which lies between the drum and the heel portion of the outer plate; the heel plate fits within a recess in the drum, and has a known taper of thickness in a direction towards the base plate. The degree of taper of the heel plate is chosen so that the knife is gripped between the clamping surface of the toe portion and the base plate by a known pressure, this known pressure corresponding to a predetermined degree of fiexure of the outer plate.

A rotating cutter constructed according to the invention will now be desecribed by way of example with reference to the accompanying drawings, of which:

FIGURE 1 shows a portion of the rotating cutter, including one knife mounted upon it so as to project slightly beyond the cylindrical surface of the cutter;

FIGURE 2 shows part of the knife and part of the toe portion of the outer plate on an enlarged scale, the toe portion being in th position at which it grips the knife with the required working pressure.

The rotating cutter comprises a generally cylindrical drum 2, having an outer surface 4 forming part of the cylindrical surface of the cutter. The drum 2 is formed with a recess 6, into which fits a heel plate 8, having a thickness which tapers from its end to its end 12, with a known degree of taper and forming a first clamping surface. This heel plate 8 has apertures 14 through it.

An outer plate 16 comprises a connecting portion 18 a rotary cutter comprises having an outer surface 20 which forms part of the cylindrical surface of the cutter, a heel portion 22 connected to the connecting portion 18 by means of screws 24, and a toe portion 26 connected to the connecting portion 18 by screws 28.

As shown in detail in FIGURE 2, the toe portion 26 has a fourth clamping surface 30 at its tip, which is separated from an intermediate surface 31 by a step 32. The surface 31 is arranged in parallel to the third clamping surface 34 of the heel portion 22, this parallel arrangement being of help when checking, testing and setting up the apparatus. The clamping surface 30 is inclined slightly relative to the surface 31 by a transverse distance of about 0.17 inch.

The outer plate 16 is clamped to the drum 2 by means of screws 36 which engage in threaded bores 38 formed in th drum 2. Each screw 36 passes through a bore 40 in the heel portion 22, and through one of the apertures 14 in the heel plate 8. The clamping surface 34 of the heel portion 22 is thus clamped against the surface of the heel plate 8, and at the same time a knife 49 is gripped between the end 47 of the clamping surface 30 of the toe portion 26 of the outer plate 16 and the second clamping surface of a base plate 42 which is mounted on the drum 2 by means of screws 44 which engage with threaded bores 46 in the drum 2. The inclination of the clamping surface 30 ensures that its actual contact with the knife is only along a narrow strip 47 at the end of the toe portion 26. The degree of taper of the heel plate 8 is indicated in FIGURE 1 by the spaced lines 48. By tightening the screw 36, the clamping surface 34 of the heel portion 22 is clamped down hard against the surface of the heel plate 8, so that the clamping surface 30 of the toe portion 26 clamps the knife 49 against the surface of the base plate 42 with a known pressure as determined by the flexing of the outer plate 16 between its heel portion 22 and its toe portion 26. The cutting edge 50 of th knife 49 projects slightly beyond the cylindrical surface of the cutter.

The rotating cutter comprises several such knives similarly mounted and spaced around the cylindrical surface of the cutter. The ends of the screws 24 and 28 are arranged to be flush with the cylindrical surface of the cutter. The heads of the screws 36 lie below the cylindrical surface, in a recess 52 formed in the connecting port-ion 18 of the outer plate 16.

Minute variations in thickness, flatness and surface finishes of the knives and accuracy of the holder reflects in the torque required to operate the feeding of the knife. Torque is in fact the criterion and it is its measurement which finally determines the taper of the heel plate.

As a measure of safety when impacted, the knife must break off along the line of grip-and the gripping arrangement is designed to accept this stress without permanent distortion or disturbance.

The knives have to be replaced at intervals of time, e.g. 24 hours, or some other known interval, and this operation has to be performed in a minimum time by a quality of labour unskilled or uninterested. in sensing niceties of grip. It is consequently necessary to be able to incorporate a dead stop locking principle which cannot be overridden, ignored or inadvertently altered.

The degree of taper is determined theoretically but if the result of tests after assembly is unsatisfactory, the appropriate heel plate is substituted. Too firm a grip shows in the rhythm of the knife feed as for example a consistent series of 0.005 inch projections every 5th feed impulse. Too slack a grip permits the knife to depart from its true path while slicing with an inconsistent width of cut as a result, followed by complete failure of the sharpening operation.

I claim:

1. A rotating cutter comprising a drum rotatable about an axis, first and second clamping surfaces associated with said drum and approximately parallel to each other, an outer plate capable of flexure and having a heel portion with a third clamping surface seatable on said first clamping surface and having a toe portion with a fourth clamping surface, said third and fourth clamping surfaces being approximately parallel to said second clamping surface, a knife gripped between the second and fourth clamping surfaces, and means clamping the heel portion to said drum for flexing said outer plate and seating said third surface hard against said first surface and forcing said toe portion with said fourth surface against said knife with a predetermined pressure independent of the pressure between the first and third surfaces.

2. A rotating cutter according to claim 1 in which the first clamping surface is formed on a heel plate which lies between the drum and the heel portion of the outer plate.

3. A rotating cutter according to claim 2 in which the heel plate fits within a recess in the drum, and tapers in thickness in a direction towards the toe portion.

4. A rotating cutter according to claim 1, including an intermediate surface on said outer plate extending between the third and fourth clamping surfaces, the third clamping surface being parallel to the intermediate surface.

5. A rotating cutter according to claim 4 in which the fourth clamping surface is inclined slightly relatively to the intermediate surface.

References Cited UNITED STATES PATENTS WILLIAM W. DYER, JR., Primary Examiner.

20 W. GRAYDON ABERCROMBIE, Examiner. 

1. A ROTATING CUTTER COMPRISING A DRUM ROTATABLE ABOUT AN AXIS, FIRST AND SECOND CLAMPING SURFACES ASSOCIATED WITH SAID DRUM AND APPROXIMATELY PARALLEL TO EACH OTHER, AN OUTER PLATE CAPABLE OF FLEXURE AND HAVING A HEEL PORTION WITH A THIRD CLAMPING SURFACE SEATABLE ON SAID FIRST CLAMPING SURFACE AND HAVING A TOE PORTION WITH A FOURTH CLAMPING SURFACE, SAID THIRD AND FOURTH CLAMPING SURFACES BEING APPROXIMATELY PARALLEL TO SAID SECOND CLAMPING SURFACE, A KNIFE GRIPPED BETWEEN THE SECOND AND FOURTH CLAMPING SURFACES, AND MEANS CLAMPING THE HEEL PORTION TO SAID DRUM FOR FLEXING SAID OUTER PLATE AND SEATING SAID THIRD SURFACE HARD AGAINST SAID FIRST SURFACE AND FORCING SAID TOE PORTION WITH SAID FOURTH SURFACE AGAINST SAID KNIFE WITH A PREDETERMINED PRESSURE INDEPENDENT OF THE PRESSURE BETWEEN THE FIRST AND THIRD SURFACES. 